When you join an existing ChosenNet network, it may
already have hundreds or thousands of members. If you start your own
network, how fast will it grow? How big
will it get?

The answer is that it can grow shockingly fast!
It depends, of course, on how many friends you invite, how quickly you get them
to sign up, how quickly they get their friends to sign up, and so forth.
The growth of your network depends on you!